Lubricating metal surfaces during cold working



Patented Nov. 7, 1950 UNITED STATES PATENT OFFICE LUBRICATING METAL SURFACES DURING COLD WORKING Albert G. Roccliini, Springdale, and Richard J. Neely, Oakmont, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa, a corporation of Delaware No Drawing. Application April 7, 1948, v Serial No. 19,647

4 Claims. (Cl. 252-49-8) phenyl phosphate; all as more fully hereinafter set forth and as claimed.

The cold working of metals, such as the cold rolling, drawing, or stamping of aluminum, stainless steel, Monel metal, and the like, is ordinarily followed by an annealing process. Annealing is often performed in a gas-fired furnace -wherein the products of combustion come in contact with the metal. Owing perhaps to the restricted space adjacent the bulk of the metal surfaces, and furthermore to the fact that'conditions in the furnace are not conducive to good combustion, it has been found that considerable staining of the metal has resulted. The stains which are formed may, in general, be classed according to three specific types. The first, a tempering stain, is believed to be an oxide formation which appears at the edge of a strip and is not thought to be dependent upon the type of lubricant employed. The second, having the appearance of a gray oxide, may appear in different positions on the strip and is believed to be caused by foreign matter such as dirt adhering to the surface and being carried on the strip into the annealing furnace. The third type of stain which may appear in streaks or spots is believed to be a carbon formation resulting when the working lubricant is subjected to the reducing atmosphere in the annealing furnace. It is the formation of the latter type of stain which the method of this invention inhibits or substantially retards.

In the past, the elimination of the stain resulting from the lubricant has been accomplished by one of several alternatives. In one embodiment, the oil stain has been eliminated by removing the lubricating oil film from the cold-worked metal with a solvent prior to the annealing step. Other embodiments have included chemically or mechanically removing the stain after theannealing operation. These embodiments, however, introduce expensive processing steps.

Y The type of lubricant employed in cold working processes has also been the subject of many prior investigations. Among the lubricants which have been used are included animal oils, vegetable oils, mineral oils, and mixtures of these and water-oil emulsions. Animal and 2 vegetable oils are effective lubricants, but they have certain disadvantages in that they are rather expensive, are not good coolants, and are easily oxidized with the resultant development of rancidity. Furthermore, animal and vegetable oils, having high carbon residue values, have been unsatisfactory in that unless they are moved from the worked metal prior-to its being annealed, they will leave stains in the form of carbon deposits on the metal when it is subsequently annealed. While straight mineral oils are satisfactory with respect to their cost, cooling properties, and stability, they, as do the animal and vegetable oils. also have a disadvantage in that unless they are removed from the worked metal prior to its being annealed; they will leave a stain on the surface of the annealed metal. Water-oil emulsions are advantageous in that they may easily be removed from metal surfaces by washing with water prior to annealing, but this step' in itself complicates the working process. Water-oil emulsions have a further disadvantage in that with repeated use as coldworking lubricants, the water tends to evaporate from the water-oil emulsions thereby changing the ratio of water to oil. Since the ratio of water to oil should be kept as uniform as possible to obtain optimum results, frequent analysis of the lubricant is required thereby adding complexity to the process.

It is the primary object achievedby this invention to provide a method of lubricating metal surfaces during cold-working by means of a lubricant which if allowed to remain on the metal during a subsequent annealing operation, will not stain the metal or deposit carbon residues thereon.

This and other objects achieved by this invention will become apparent in the following detailed description thereof.

According to our invention, the surfaces of a metal being worked are lubricated by establishing and maintaining thereon a film of lubricant comprising i a petroleum lubricating oil which would normally tend to stain said metal surfaces during annealing. thereof and a small amount, suflicient to substantially retard the formation of stain on the metal when it is subsequently annealed. of a chlorophenyl phosphate. As examples of the chlorophenyl phosphates which may be used in accordance with our invention may be included diphenyl mono(ortho-chlorophenyl)- phosphate, diphenyl mono(para-chlorophenyl)-- phosphate. di(ortho-chlorophenyl) mono-phenyl phosphate, tri-ortho-chlorophenyl phosphate,

These compounds are advantato a petroleum lubricating oil of the roll oil and draw oil type in an amount between about 0.01 and 1.0 per cent by weight of the oil. While these compounds may be added to an oil in an amount greater than about 1.0 per cent without deleteriously modifying the lubricating properties of the oil, it is not ordinarily desirable from an The exact amount of compound employed will depend upon the particular compound used as well as the particular metal being worked.

In the practice of our invention any suitable lubricating oil base, whether it is derived from a paraflinic, naphthenic, or mixed base crude, may be employed. Although it is seldom necessary in compositions of the type disclosed herein,

and the likegeously added the lubricating oil base may contain one or more.

of the so-called additive agents including oiliness and extreme pressure agents, viscosity index improvers, pour point depressants, detergents, foam inhibitors, and corrosion and oxidation inhibitors. The particular lubricant chosen depends on the type of cold-working operation for which it is intended. For example, oils used in cold rolling are generally highly refined and are relatively volatile having viscositles between about 50 and 200 SUV at 100 F., whereas oils used in drawing operations may have viscosities as high as 5000 SUV at 100 F. It is not intended to limit this invention with respect to the particular lubricating oil base.

The advantages to be obtained in accordance with our invention are illustrated in the following comparative laboratory tests made on a highly refined naphthenic base oil having a Saybolt Universal Viscosity of 53 at 100 F. and.the same oil containing a small amount of a chlorophenyl phosphate, namely, mono(ortho-chlorophenyl)- phosphate. To simulate actual operating conditions of the annealing of cold-rolled aluminum, 1 ml. of the oil to be tested was placed between two aluminum plates (99.2% aluminum). The aluminum plates were then placed in a muilie furnace for 30 minutes at a temperature of 650 F., this being the temperature of the metal as determined by a thermocouple. The plates were then removed and inspected. The appearance of the aluminum after annealing, as tabulated hereinbelow, was determined by visual inspection and comparison with a blank set of plates.

Per cent by Weight diphenyl Appearance of Lubrlcatmg Composition mno(0rtho- A uminum chlorophenyl)- alter Annealing phosphate Base Oil (53 SUV at 100 F.) 0 Severe Stain. Do 0. 025 No Stain.

0.05 Do. 0. 25 Spot Stains. l. 0 No Stain.

1 Stain caused by foreign matter.

economic standpoint.

steel. particularly when such metals are to be annealed after cold working, and where it is desirable that the surfaces of such metals be clean and bright after annealing. The method of our invention obviates the expensive step of removing the oil film from the metal prior to its being annealed and, at the same time, overcomes the staining which normally would occur in the annealing operation when employing a straight mineral lubricating oil as a lubricant for the cold working of metals.

While our invention has been described herein with particular reference to certain specific embodiments thereof by way of illustration, it is to be understood that the invention is not limited.

to such embodiments except as hereinafter defined in the appended claims.

We claim:

1. In cold working a metal subsequently to be annealed, the improvement which comprises lubricating the surfaces of the metal being worked by establishing and maintaining thereon a film of lubricant comprising a petroleum lubricating oil which would normally tend to stain said metal surfaces during annealing thereof and between about 0.01 and 1.0 per cent by weight of a chlorophenyl phosphate selected from the group consisting of. diphenyl mono(ortho-chlorophenyl)- phosphate and diphenyl mono(para-chlorophenyl) phosphate. g

2. In cold working a metal subsequently to be annealed, the improvement which comprises lubricating the surfaces of the metal being worked by establishing and maintaining thereon a film of lubricant comprising a petroleum lubricating oil which would normally tend to stain said metal surfaces during annealing thereof and between about 0.01 and 1.0 per cent by weight of diphenyl mono(ortho-chlorophenyl) phosphate.

3. In cold working a metal subsequently to be annealed, the improvement which comprises lubricating the surfaces of the metal being worked by establishing and maintaining thereon a film of lubricant comprising a petroleum lubricating oil which would normally tend to stain said metal surfaces during annealing thereof. and-between about 0.01 and 1.0 per cent by weight of diphenyl mono(para-chlorophenyl) phosphate.

4., In cold rolling aluminum subsequently to be annealed, the improvement which comprises lubricating the surfaces of the aluminum being rolled by establishing and maintaining thereon a film of lubricant comprising a highly refined relatively volatile petroleum lubricating oil which would normally tend to stain, said aluminum surfaces during annealing thereof and between about 0.01 to 1.0 per cent by weight of diphenyl mono- (ortho-chlorophenyl) phosphate.

ALBERT G. ROCCHINI. RICHARD J. NEELY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Hoelscher Nov. 4, 1947 

1. IN COLD WORKING A METAL SUBSEQUENTLY TO BE ANNEALED, THE IMPROVEMENT WHICH COMPRISES LUBRICATING THE SURFACES OF THE METAL BEING WORKED BY ESTABLISHING AND MAINTAINING THEREON A FILM OF LUBRICANT COMPRISING A PETROLEUM LUBRICATING OIL WHICH WOULD NORMALLY TEN TO STAIN SAID METAL SURFACES DURING ANNEALING THEREOF AND BETWEEN ABOUT 0.01 AND 1.0 PER CENT BY WEIGHT OF A CHLOROPHENYL PHOSPHATE SELECTED FROM THE GROUP CONSISTING OF DIPHENYL MONO(ORTHO-CHLOROPHENYL)PHOSPHATE AND DIPHENYL MONO(PARA-CHLOROPHENYL) PHOSPHATE. 